GONIOCYSTIS. 355 



Hab. Dolgelly aud Penzance : Mr. Ralfs. 

 This Staurastrum is to be distinguished from the previous 

 species by the trifid extremities of the rays. 



4. Staurastrum ? bifidum Ralfs. 

 Plate LXXXV. Fig. 2. 



Chai: Frond smooth^ hut little constincted in the centre, truncate 

 laterally. Rays trijid. End view triradiate. 

 Desmidium bijidum Ehr., Die Infus. p. 141. t. 10. f. 11. ; 



Ealfs, I.e. p. 151. pi. X. fig.3. 

 Hab. Dolgelly and Penzance : Mr. Ralfs. 



The smoothness of the frond will always distinguish this 

 from the previous species. It should probably be referred to 

 Trifjonocystis. 



Section iii. Pentasterias Ehr. 



Char. Frond in front view without diverging processes. End 

 view circular, with usually five rays. 

 Derivation. From TrsvTs^five, and aarepia?, starred. 



1. Pentasterias arachnis Ilass. 

 Plate LXXXV. Fig. 8. 



Char. Frond rough, deeply constricted in the centre. Seg- 

 ments about as long as broad, sid) orbicular, with elongated 

 slender hyaline and incurved processes. End view Jtvc- 

 rayed. ■ 

 Staurastrum Arachne Ealfs, in Annals, vol. xv. p. 157. 



pi. xi. fig. 6. 

 Hab. Boggy pool near Dolgelly, \cvy rare : Mr. Ralfs. 



" This plant is remarkable for its slender processes which 

 will easily distinguish it from St. mnrgaritaceum. It cannot 

 be a five-rayed variety of St. gracile, for the rays arc longer, 

 more slender, remarkably incurved, and also entire at the 

 extremity." — Ralfs. 



s. K 2 



